RADIOACTIVE INDICATORS IX BIOCHEMISTRY 



991 



NyLiN(53) made a very extended application of the method described. 

 He determined, besides the total circulating erythrocyte volume, that 

 of single organs such as lungs and legs. A blood sample of a human 

 subject was secured and labelled with 32p ^s described above. Before 

 injection of an aliquot of the labelled red corpuscles into the subject, 

 the vessels were clamped. The red corpuscles circulating in the legs 

 were thus prevented from participating in the "dilution" of the injected 

 labelled erythrocytes, which takes place after injection of labelled red 



400 

 360 

 360 



Circulation fo the legS released 



Red blood corpuscles 



Plasma 



Circulat. bl. volume 



leiOgr 



2790" 



4600" 



27gr/kg 



42 « 



69 II 



1645 ml 



2730 " 



4405" 



25 ml/ kg 



41 " 



66 



10 



20 30 40 



Minutes after injection 



50 



60 



Fig. 13. — Determination of the circulating corpuscle (blood) 

 volume of the legs (Nylin) (reproduced, with permission, from Ark. 



Kemi 20, A No. 17 (1945). 



corpuscles into the non-radioactive circulation and the extent of which 

 indicates the amount of circulating erythrocytes. As seen in Fig. 13, 10 

 minutes after injection of labelled corpuscles, the amount of circulating 

 erythrocytes, excluding that of the legs, is found from the "dilution" 

 figures to be 1560 gm. After removal of the clamps, there was a marked 

 decrease in the activity of a 1 gm sample of corpuscle (denoted in Fig. 13 

 as specific activity). Owing to the participation of the red corpuscles of 

 the leg in the "dilution" process, the specific activity of the corpuscles 

 decreases from 550 to 428, indicating that the red corpuscle volume of 

 the body, which now includes that of the legs as well, amounts to 1810 

 gm From the above figures the weight of the erythrocytes circulating 

 in the legs is determined to be 250 gm. 



The labelling of a red corpuscle sample in vitro is made possible by 

 the presence in the red corpuscles of an enzymic mechanism which i- 

 instrumental in alternately degrading and building up the comparatively 

 large amounts of labile organic phosphorus compounds in the erythros 



